On Mon, 1 Aug 2016 16:59:23 +0200 Alexander Potapenko <glider@xxxxxxxxxx> wrote:
> If the total amount of memory assigned to quarantine is less than the
> amount of memory assigned to per-cpu quarantines, |new_quarantine_size|
> may overflow. Instead, set it to zero.
>
> --- a/mm/kasan/quarantine.c
> +++ b/mm/kasan/quarantine.c
> @@ -214,7 +214,15 @@ void quarantine_reduce(void)
> */
> new_quarantine_size = (READ_ONCE(totalram_pages) << PAGE_SHIFT) /
> QUARANTINE_FRACTION;
> - new_quarantine_size -= QUARANTINE_PERCPU_SIZE * num_online_cpus();
> + percpu_quarantines = QUARANTINE_PERCPU_SIZE * num_online_cpus();
> + if (new_quarantine_size < percpu_quarantines) {
> + WARN_ONCE(1,
> + "Too little memory, disabling global KASAN quarantine.\n",
> + );
> + new_quarantine_size = 0;
> + } else {
> + new_quarantine_size -= percpu_quarantines;
> + }
> WRITE_ONCE(quarantine_size, new_quarantine_size);
>
> last = global_quarantine.head;
This is a little tidier:
--- a/mm/kasan/quarantine.c~kasan-avoid-overflowing-quarantine-size-on-low-memory-systems-fix
+++ a/mm/kasan/quarantine.c
@@ -217,14 +217,11 @@ void quarantine_reduce(void)
new_quarantine_size = (READ_ONCE(totalram_pages) << PAGE_SHIFT) /
QUARANTINE_FRACTION;
percpu_quarantines = QUARANTINE_PERCPU_SIZE * num_online_cpus();
- if (new_quarantine_size < percpu_quarantines) {
- WARN_ONCE(1,
- "Too little memory, disabling global KASAN quarantine.\n",
- );
+ if (WARN_ONCE(new_quarantine_size < percpu_quarantines,
+ "Too little memory, disabling global KASAN quarantine.\n"))
new_quarantine_size = 0;
- } else {
+ else
new_quarantine_size -= percpu_quarantines;
- }
WRITE_ONCE(quarantine_size, new_quarantine_size);
last = global_quarantine.head;
_
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